Four-membered photographic wide-angle objective



JUL 28 1958 J. LAUTENBACHER Erm. 2,821,112

FOUR-MEMBERS!) PHOTOGRAPHIC WIDE-ANGLE OBJECTIVE Filed March 5, 1956` Inventors Johan/:Lautenbadwer nepdor Bren i del M @Mouw ATTOYN EBS United States Patent Oce FOUR-MEMBERED PHOTOGRAPHIC WIDE-ANGLE OBJECTIVE Johann Lantenbacher and Theodor Brendel, Munich, Germany, assignors to Enna-Werk Optische Anstalt Dr. Appelt K. G., Munich, Germany, a corporation of Germany Applicalion March 5, 1956, Serial No. 569,500

2 Claims. (Cl. 88-57) This invention relates to a four-membered photographic wide-angle objective, and refers more particularly to an objective of this type which consists of a simple triplet and a negative menscus located in front of the triplet and having a concave surface which is directed toward the triplet, the menscus and the triplet being separated by an air gap, the length of which is substantially greater than the over-al1 length of the triplet.

In prior art objectives of this type were used in single reex cameras due to their long back focal length, and they were corrected for a relative aperture up to f:4.0.

An object of the present invention is to improve objectives of this type.

Another object of the present invention is the provision of a. wide-angle objective of the described type wherein the relative aperture is enlarged to f:3.5.

Yet another object is to improve simultaneously the comatie corrections of such objectives even for a large wave-length range to such an extent that the diameters for oblique rays may be substantially widened in order to reduce the so-called vignetting.

Other objects of the present invention will become apparent in the course of the following specification.

'I'he objects of the present invention may be realized by a specific design of an objective, the construction data of which, namely the radii r1 to ra, the axial thicknesses d1 to d4, the air gaps or air spaces l1 to la, the refractive indices n; to n4 and the Abbe v-values v1 to v4 are located within the following ranges:

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing, the single figure of which shows, by way of example, an objective constructed in accordance with the present invention.

The drawing gure illustrates a negative menscus M and a simple triplet T. All the data of this construction 2,821,112 Patented Jan. 28, 1958 lie within the above stated range. The objective has a focal length of f=1.0 and the back focal length is s'\=1.01941.

In the following example and in the drawing, the radii are designated as r, the axial thicknesses are designated as d, the air gap spaces as l, the refractive indices for the yellow helium line of the spectrum (587.6 my.) as n, and the Abbe-numbers as v:

in relation to the thicknesses d, to d4 of the members, the air gaps l, to I3 between the members with reference to the focal length f,

in relation to the refractive indices n1 to n4 of the members,

and in relation to the Abbe-numbers v1 to v4 of'the 2. An objective in accordancc with claim 1, having the following constructional data,

References Cited in the le of this patent UNITED STATES PATENTS 

